1. Field of the Invention
The present invention relates to a cup attaching apparatus for attaching a cup, used for fixing an eyeglass lens to an eyeglass lens processing apparatus, to the lens.
2. Description of Related Art
There is a cup attaching apparatus called a blocker for attaching a cup, used for fixing an eyeglass lens to an eyeglass lens processing apparatus, to the lens. This cup attaching apparatus comprises a blocking arm provided with a cup holder in the vicinity of a distal end of the arm, the holder being used to hold the cup, and a lens mount (a lens support) on which the lens is to be mounted. When the lens is mounted on the mount, the cup is mounted (fitted) in the holder, and the arm is moved downward, the cup is attached to a front refractive surface of the lens.
Such attaching apparatus is commonly arranged to support a rear refractive surface of the lens with at least three support pins fixedly provided on the mount. A supporting plane defined by the support pins is horizontal and therefore the lens can be supported stably. Thus, even after an operator moves his/her hand off the lens, the cup can be attached to the front refractive surface of the lens.
Meanwhile, in the case where the cup is to be attached to the lens having the rear refractive surface different in shape from the front refractive surface, such as a prism lens and an astigmatic lens (a toric lens), the following problem may arise. When the rear refractive surface of the lens is supported by the support pins fixed with the supporting plane being held in the horizontal position, the front refractive surface of the lens tends to incline, which is likely to cause errors in positioning accuracy in attaching the cup. To avoid such problems, a cup attaching apparatus having a mechanism arranged to simultaneously move the support pins up and down (e.g., WECO CENTERING SYSTEM by WECO OPTICAL MACHINERY, German) has also been proposed.
However, if the supporting plane is allowed to incline by the vertical movement of the support pins, the supported lens is likely to drop off the support pins unless the lens is pressed from above.